I want to find out what a unit's armor value is through triggers, how do I do this? I will then be adding, removing and performing various effects depending on the outcome of course, so any and all ways to find it out (not just through triggers) would be great!

You just want to check using a condition? That would be as simple as comparing the value. The condition is called "Unit Property" and you can make the comparison like so:

If you mean firing a trigger when the unit's armor hits a certain value, you'd either have to make a custom event or just have a trigger that periodically checks the value (if the armor can only change through upgrades, having a trigger with an event for an upgrade completing would be an optimal way of approaching this).

In the end I may not need this, the entire reason for it is gone since I realized that I can just detect each individual scenario that would change armor anyway, most of the time that may even be through data. So I think the problem is resolved.